Optical rotary joints for the simultaneous transmission of several channels usually use a derotating optical element such as, for example, the one including now abandoned a Dove prism. U.S. Pat. No. 5,371,814 discloses an example of such rotary joint. Here, GRIN lenses are used to collimate the light from glass fibers. The lenses must be individually adjusted. An improvement can be achieved by combining a plurality of fibers with a common fiber holder to form a fiber array. Such a fiber array is disclosed, for example in US 2004/0165854 A1. The fibers are shown to be aligned in V grooves and fixed with a retaining plate. A Dove prism, which has a circular imaging area, cannot be effectively used with a linear fiber arrangement according to this document. An improvement, disclosed in U.S. Pat. No. 6,704,483 B2, is based on a plurality of one-dimensional fiber arrays that are held with respect to one another by a precise but structurally complex holder with means for alignment of the individual fiber arrays.